1. Field of the Invention
The present invention relates to a pump device.
2. Discussion of Related Art
JP-A-8-104214 discloses a pump device including a pump, an electric motor for driving the pump, and a pressure relief valve arranged to discharge a pressurized fluid delivered from the pump to a low-pressure reservoir when the delivery pressure of the pump (pressure of the pressurized fluid) exceeds a preset relief pressure. The pressure relief valve prevents an excessive rise of the delivery pressure of the pump, thereby protecting the electric motor from an overload.
In the pump device described in the above-identified publication, the pump is kept operated so as to maintain the delivery pressure at the present relief pressure, even after the delivery pressure has been raised to the present relief pressure. This continuous operation of the pump requires a comparatively large amount of consumption of an electric energy by the electric motor to drive the pump.
It is therefore an object of the present invention to provide a pump device which is arranged to reduce the required amount of consumption of an electric energy. This object may be achieved according to any one of the following modes of the present invention, each of which numbered like the appended claims and depends from the other mode or modes, where appropriate, for easier understanding of technical features disclosed in the present application, and possible combinations of those features. However, it is to be understood that the invention is not limited to those technical features or combinations thereof, and that any one of a plurality of technical features described below with respect to any one mode of the invention may be a subject of the present invention, without the other technical feature or features being combined with that one feature.
(1) A pump device comprising a support member having a fitting recess, and a movable member which is reciprocated in said fitting recess to suck a working fluid, pressurize the fluid and deliver the pressurized fluid, the pump device comprising a movement restricting device operable to deform a wall at least partially defining the fitting recess of the support member, such that the wall is deformed toward the movable member, for restricting a reciprocating movement of the movable member in the fitting recess, at least when an amount of the pressurized fluid required to be delivered by the pump device is smaller than a nominal delivery amount of the pump device.
In the pump device according to the above mode (1) of this invention, the movement restricting device is operated, when the amount of the pressurized fluid required to be delivered by the pump device is smaller than the nominal delivery amount of the pump device, so that the wall of the support member which at least partially defines the fitting recess (such as a fitting hole or bore in a cylinder in a piston pump or a vane groove in a vane pump) is deformed toward the movable member, for restricting a reciprocating movement of the movable member in the fitting recess. For instance, the movement restricting device is arranged to inhibit or prevent the reciprocating movement of the movable member, reduce a speed of the movement, or reduce the reciprocating stroke of the movable member, when the pump device is not required to deliver the pressurized fluid. For example, the wall of the support member is elastically deformed toward the fitting recess, for zeroing the clearance between the movable member and the wall of the support member, and applying a pressing force from the wall to the movable member in a direction intersecting the direction of reciprocating movement of the movable member (e.g., in a direction perpendicular to the direction of movement). When a force of friction between the wall and the movable member which is produced on the basis of the pressing force becomes larger than a force by which the movable member is moved, the movement of the movable member is inhibited or prevented. Namely, the movable member is held stationary, with the wall held in pressing contact with the outer surface of the movable member. Alternatively, the wall of the support member is elastically deformed such that a portion of the wall projects toward the movable member, so that the projecting portion engages the movable member to limit a distance of movement of the movable member, for thereby reducing the reciprocating stroke of the movable member.
When the movement of the movable member in the fitting recess is inhibited, the pump device is not capable of delivering the pressurized fluid. In this case, the pressure of the fluid in a discharge port of the pump device in a pump chamber formed in front of the movable member is either lowered or maintained at a level before the movement is inhibited. Whether the fluid pressure is maintained or lowered depends upon a type of a fluid-operated device which is operated by the pressurized fluid delivered from the pump device, for instance. Where the fluid-operated device does not consume the pressurized fluid, the fluid pressure in the discharge port or pump chamber is maintained. Where the fluid-operated device consumes the pressurized fluid, the fluid pressure is lowered.
Where the reciprocating stroke of the movable member is reduced by the movement restricting device, the amount of the pressurized fluid delivered from the pump device during one reciprocation of the movable member is reduced. Accordingly, the rate of increase of the fluid pressure in the discharge port or pump chamber is reduced, or the fluid pressure is maintained or is lowered. Whether the rate of increase of the fluid pressure is reduced or the fluid pressure is maintained or lowered depends upon a relationship between the amount of consumption of the pressurized fluid by the fluid-operated device and the amount of the pressurized fluid delivered by the pump device.
In any case, an increase of the fluid pressure in the discharge port or pump chamber of the pump device can be restricted by the movement restricting device, so that the amount of electric energy required to move the movable member can be reduced. Further, a pressure relief valve provided in the conventional pump device is not essential, in the presence of the movement restricting device. However, the principle of the present invention does not exclude the provision of such a pressure relief valve for improving the operating safety of the pump device.
The movement restricting device may be arranged to deform either a portion or an entirety of the wall partially defining the fitting recess in the support member. Namely, the wall is required to be deformed such that the diameter of at least a portion of the wall (inside diameter of the fitting recess) is reduced to be smaller than the outside diameter of the movable member. Where the wall is deformed partially, the wall may have only one deformable portion or a plurality of deformable portions. For example, the wall has a deformable cylindrical portion which is deformed by the movement restricting device, in a direction intersecting the direction of movement of the movable member. However, the deformable portion is not limited to such a cylindrical portion of the wall.
Whether the pump device is required to deliver the pressurized fluid or not, that is, whether the movement restricting device should be operated or not, depends upon an operating condition of either the pump device per se or the fluid-operated device. For example, the movement restricting device is operated when it is not desirable to operate the pump device after the delivery pressure has reached a predetermined level, or when the fluid-operated device does not require the pressurized fluid whose pressure is higher than a predetermined level.
The principle of the present invention is applicable to a gas pump arranged to pressurize a gas, and a liquid pump arranged to pressurize a liquid. However, the present invention is more suitably applicable to the liquid pump, since a large pressing force may be applied to the wall of the support member in the liquid pump than in the gas pump.
(2) A pump device according to the above mode (1) wherein the movement restricting device includes a hydraulically operated movement restricting device operable to deform the wall, on the basis of a pressure of the pressurized fluid delivered by the pump device.
In the pump device according to the above mode (2), the wall of the support member is deformed on the basis of the pressure of the pressurized fluid delivered by the pump device. Thus, the pressurized fluid delivered by the pump device is utilized to operate the movement restricting device. In this mode, the movement restricting device does not use an exclusive drive device for causing deformation of the wall.
(3) A pump device according to the above mode (1) or (2), wherein the movement restricting device is operable to deform the wall when a pressure of the pressurized fluid delivered by the pump device becomes higher than a predetermined value.
In the pump device according to the above mode (3), it is considered that the pump device is not required to deliver the pressurized fluid, after the pressure of the pressurized fluid delivered by the pump device has exceeded the predetermined value. That is, the movement restricting device is operated to deform the wall when the pressure of the delivered pressurized fluid becomes higher than the predetermined value. In this case, the movement restricting device may be arranged to deform the wall so as to inhibit the movement of the movable member, after the delivery pressure of the pump device becomes higher than the predetermined value.
(4) A pump device according to any one of the above modes (1)-(3), wherein the movement restricting device permits the movement of the movable member when the pump device is required to deliver the pressurized fluid, and inhibits the reciprocating movement of the movable member when the pump device is not required to deliver the pressurized fluid.
In the pump device according to the above mode (4), the wall of the support member is deformed to inhibit the reciprocating movement of the movable member when the pump device is not required to deliver the pressurized fluid.
(5) A pump device according to anyone of the above modes (1)-(4), wherein the movement restricting device is operable to deform the wall for inhibiting the movement of the movable member located at a predetermined position while the pump device is not required to deliver the pressurized fluid.
The movement restricting device may be arranged to deform the wall of the support member for inhibiting the movement of the movable member when the movable member is located any desired position in the direction of the reciprocating movement of the movable member. For instance, the movement restricting device is desirably arranged to inhibit the movement of the movable member located at its fully advanced position or upper dead point.
(6) A pump device according to any one of the above modes (1)-(5), wherein the movement restricting device is operable to deform said wall to make a reciprocating stroke of said movable member smaller when the amount of the pressurized fluid required to be delivered by the pump device is smaller than the above-indicated nominal delivery amount.
The amount of the pressurized fluid to be delivered by one reciprocating movement of the movable member of the pump device is reduced by reducing the reciprocating stroke of the movable member. For instance, the reciprocating stroke of the movable member is reduced so that the amount of the pressurized fluid delivered from the pump device is substantially equal to the amount of consumption of the pressurized fluid. This arrangement reduces an increase in the delivery pressure of the pump device.
(7) A pump device according to any one of the above modes (1)-(6), wherein the support member includes a cylinder having as the above-indicated wall a cylindrical portion which partially defines a cylinder bore as the above-indicated fitting recess, and the movable member includes a piston reciprocably fitted in the cylinder bore, the cylindrical portion having an outer circumferential surface partially defining a pressure chamber which receives the pressurized fluid through a fluid-introducing portion.
In the pump device according to the above mode (7), the pressurized fluid delivered by the pump device is introduced into the pressure chamber. The cylindrical portion of the cylinder is elastically deformed when the pressure of the fluid in the pressure chamber is higher than a predetermined level. With the elastic deformation of the cylindrical portion, a clearance between the inner circumferential surface of the cylindrical portion and the outer circumferential surface of the piston is zeroed, and the cylindrical portion is forced against the outer circumferential surface of the piston. As a result, a pressing force is applied from the cylindrical portion to the piston in a direction intersecting the direction of movement of the piston. When a force of friction between the cylindrical portion and the piston on the basis of this pressing force becomes larger than a force by which the movable member is moved, the movement of the piston is inhibited. The cylindrical portion of the cylinder may be elastically deformed such that a portion of the cylindrical portion projects radially inwardly of the cylinder bore, that the projecting portion functions to limit a distance of movement of the piston. In this case, the operating stroke of the piston is reduced. The configuration and size of the projecting portion may be changed or determined by the configuration of the pressure chamber. The size and configuration of the projecting portion may be changed with an increase of the fluid pressure in the pressure chamber. Where the movable member includes an engaging portion for engagement with the projecting portion of the cylindrical portion such that the position at which the movement of the movable member is inhibited is determined by a relative position between the engaging portion and the projecting portion, a change of the size and/or configuration of the projecting portion changes the relative position of the engaging portion and the projecting portion, thereby changing the position at which the movement of the movable member is inhibited. Even where the movable member does not include an engaging portion, the force of friction between the cylindrical portion and the movable member increases with an increase of the size of the projecting portion, which results in an increase in the surface area of contact of the projecting portion with the movable member. In this case, the movement of the movable member is inhibited when the force of friction determined by the surface area of contact of the projecting portion and the movable member becomes larger than the force by which the movable member is moved.
The pressure chamber may be formed over the entire axial length of the cylindrical portion of the cylinder, or over a portion of the axial length. The pressure chamber may be formed by utilizing a gap provided between the cylindrical portion of the cylinder and a housing in which the cylinder is fixedly received. Where the cylindrical portion is relatively easily elastically deformed, the fluid pressure in the pressure chamber which is required to elastically deform the cylindrical portion is relatively low. The ease of elastic deformation is determined by the material, configuration and other factors of the cylindrical portion.
(8) A pump device according to the above mode (7) comprising: a fluid sucking portion and a fluid discharging portion which are spaced apart from each other in an axial direction of the piston; a housing in which the cylinder is fitted; and at least one sealing member disposed between the housing and the cylindrical portion of the cylinder and isolating the fluid sucking portion and said fluid discharging portion.
In the pump device according to the above mode (8), the fluid sucking portion and the fluid discharging portion are disposed such that these portions are spaced apart from each other in the axial direction of the position, and the cylinder and the housing are mutually separate members. Further, the sealing member or members is/are disposed between the cylinder and the housing, to prevent a flow of the pressurized fluid from the fluid discharging portion into the fluid sucking portion through a gap between the cylinder and the housing.
Since the cylinder is formed separately from the housing, the cylinder can be easily designed so as to permit the piston to be slidably movable in the cylinder bore in an intended manner. In other words, it is not required to design both of the housing and the cylinder, so as to permit intended slidable movement of the piston in the cylinder bore, whereby the cost of manufacture of the pump device can be reduced. In designing the cylinder, for example, the material of the cylinder must be taken into account so that the cylinder has a sufficiently high degree of wear resistance, and/or the cylinder must be manufactured so that the sliding surface of the cylinder has a low friction coefficient.
(9) A pump device according to the above mode (8), wherein the pressure chamber consists of a portion of a gap between the cylinder and the housing, which portion is located on one side of the at least one sealing member that is nearer to the fluid discharging portion.
The pump device according to the above mode (8) wherein the pressure chamber is formed by utilizing the gap between the cylinder and the housing can be manufactured with a comparatively small amount of increase of the manufacturing cost due to the provision of the movement restricting device. Where the gap between the cylinder and the housing has an opening communicating with the fluid discharging portion, this opening serves as a part of the fluid-introducing portion described above with respect to the above mode (7).
(10) A pump device according to the above mode (8) or (9), wherein the above-indicated at least one sealing member includes a sealing member located on one side of a front axial end of the piston which one side is nearer to the fluid sucking portion when the piston is located at a fully advanced position thereof on the side of the fluid discharging portion, the above-indicated front axial end being located on the side of the fluid discharging portion.
In the pump device according to the above mode (10), the movement of the piston can be inhibited with high stability at any position in the reciprocating stroke of the piston. The length of the fluid chamber in the axial direction of the piston can be increased with an increase of a distance between the sealing member and the axial end of the piston when the piston is located at its fully advanced position. For a given fluid pressure in the fluid chamber, the force to be applied from the cylindrical portion of the cylinder to the cylinder increases with an increase in the length of the fluid chamber. The fluid pressure in the pressure chamber becomes highest when the piston is moved to its fully advanced position (upper dead point). Therefore, the movement of the piston is usually inhibited when the piston is located at its fully advanced position.
(11) A pump device according to any one of the above modes (8)-(10), wherein the at least one sealing member includes a sealing member located at a position which is on one side of a midpoint between axial opposite axial ends of the piston when the piston is located at a fully advanced position thereof on the side of the fluid discharging position, the above-indicated one side of the midpoint being nearer to a fully retracted position on the side of the fluid sucking portion.
The sealing member may be located such that a distance from the position of the sealing member to the axial end of the piston on the side of the fully advanced position is at least ⅔ or xc2xe of the axial length between the opposite axial ends of the piston.
The sealing member disposed between the cylinder and the housing may be located at a position on one side of the axial ends of the piston located at its fully advanced position (upper dead point), which one side is nearer to the fully retracted position (lower dead point). In this case, the movable member preferably includes a large-diameter portion serving as the piston, and a small-diameter portion serving to transmit a drive force from a drive device to the piston. The small-diameter portion may be considered to be a piston rod connected to the piston.
(12) A pump device according to any one of the above modes (7)-(11), wherein at least one of an outer circumferential surface of the cylinder and an inner circumferential surface of the housing has at least one recess each of which provides said pressure chamber.
Only the outer circumferential surface of the cylinder or only the inner circumferential surface of the housing may has at least one recess. Alternatively, both of those outer and inner circumferential surfaces have recesses. In this latter case, the recesses formed in the outer and inner circumferential surfaces may cooperate to define a single recess, or may be spaced apart from each other in the axial direction of the cylinder. In any case, at least one of the cylinder and the housing has a single recess or a plurality of recesses, which is/are easily formed. While each recess is preferably an annular recess, the recess may be an arcuate or part-circumferential recess corresponding to a part of the circumference of the above-indicated circumferential surfaces. Alternatively, the recess may be a generally elongate recess or groove formed so as to extend in the axial direction of the cylinder (piston).
Where a recess is formed in the outer circumferential surface of the cylinder, a relatively thin-walled cylindrical wall is formed radially inwardly of this recess. This thin-walled cylindrical wall is easily deformable. That is, the formation of a recess in the outer circumferential surface of the cylinder provides an easily deformable cylindrical wall serving as the wall which partially defines the fitting recess in which the piston is slidable fitted and which is deformed by the fluid pressure in the pressure chamber. The thickness of the easily deformable cylindrical wall can be changed by changing the depth of the recess.
(13) A pump device according to the above mode (7), comprising a fluid sucking portion and a fluid discharging portion which are spaced apart from each other in an axial direction of the piston, and wherein the cylinder further has an annular groove which has an annular shape in transverse cross section of the cylinder and a diameter larger than the cylinder bore, the annular groove extending in an axial direction of the cylinder and having a closed end on the side of the fluid sucking portion, and an open end on the side of the fluid discharging portion, the annular groove and the cylinder bore cooperating with each other to define therebetween the cylindrical portion serving as the above-indicated wall, the annular groove providing the pressure chamber.
In the pump device according to the above mode (13), the annular groove is formed in the cylinder of the support member, and this annular groove cooperates with the cylinder bore to define therebetween the cylindrical portion serving as the cylindrical wall to be elastically deformed. This arrangement does not require a sealing member for isolating the fluid sucking portion and the fluid discharging portion from each other.
(14) A pump device according to any one of the above mode (1)-(13), wherein the movement restricting device includes a switching device operable between a first state for permitting deformation of the above-indicated wall and a second state for inhibiting the deformation of the wall.
The switching device may include a valve device operable between a first state for permitting a flow of the pressurized fluid into said pressure chamber and a second state for inhibiting the flow.
The valve device indicated above may include an electromagnetic valve provided in a fluid passage connecting a fluid discharging portion of the pump device and said pressure chamber. The electromagnetic valve is switchable between a state for permitting the flow of the pressurized fluid from the fluid discharging portion into the pressure chamber and a sate for inhibiting this flow. The movement of the movable member can be rapidly stopped by switching the electromagnetic valve to the state for permitting the fluid flow into the pressure chamber when the fluid pressure in the fluid discharging portion has increased to a level at which the movement of the movable member can be inhibited. The electromagnetic valve is desirably switched to the state for permitting the fluid flow when the movable member has moved to its fully advanced position or upper dead point.
The valve device may include a pressure relief valve provided in the fluid passage connecting the fluid discharging portion and the pressure chamber. The pressure relief valve is arranged to inhibit the fluid flow from the fluid discharging portion into the pressure chamber when the fluid pressure in the fluid discharging portion is not higher than a predetermined relief pressure, and permits this fluid flow when the fluid pressure is higher than the relief pressure. Where the relief pressure is determined to be a level at which the movement of the movable member can be inhibited, the movement of the movable member can be inhibited as soon as the pressure relief valve is opened.
(15) A pump device according to any one of the above modes (1)-(14), wherein the movement restricting device includes a buffer device operable to reduce a change of the pressure of the pressurized fluid to be delivered by the pump device.
In the pump device according to the above mode (15), the pressure of the pressurized fluid delivered by the pump device is transmitted to the pressure chamber, with a change of the fluid pressure being reduced by the buffer device. The buffer device is effective to prevent an abrupt rise of the fluid pressure in the pressure chamber, which would take place upon an abrupt rise of the fluid pressure in the fluid discharging portion. Accordingly, the buffer device prevents an abrupt increase of the force to be applied to the movable member and the wall. The buffer device is particularly effective where the working fluid is a liquid. In other words, there is a relatively low need to provide the buffer device, where the working fluid is a compressible gaseous fluid.
The buffer device may be disposed between the fluid discharging portion and the pressure chamber, or between the fluid discharging portion and a fluid-actuator device which is operated by the pressurized fluid delivered by the present pump device. For example, the buffer device is desirably arranged to be able to accommodate the volume of the pressurized fluid that is delivered by one reciprocating movement of the movable member. The fluid-actuated device may serve as the buffer device.
(16) A pump device according to any one of the above-indicated modes (1), (4)-(6) and (14), wherein said movement restricting device includes an electromagnetically operated device which includes a coil and which produces an electromagnetic force for deforming the above-indicated wall, upon energization of said the with an electric current.
In the pump device according to the above mode (16), the wall of the support member is deformed by an electromagnetic force produced by the electromagnetically operated device. For instance, the electromagnetic force acts on the wall in a radially inward direction of the fitting force.
(17) A pump device according to any one of the above modes (1)-(16), further comprising:
a drive device operable in contact with the movable member, to advance the movable member in an advancing direction; and
a biasing device biasing the movable member in a retracting direction opposite to the advancing direction, for forcing the movable member onto the drive device.
In the pump device according to the above mode (17), the movable member is advanced by the drive device, against a force based on the fluid pressure in a pump chamber, and a biasing force of the biasing device. When the drive force produced by the drive device does not act on the movable member after the movable member has been advanced to its fully advanced position or upper dead point. Accordingly, the movable member is retracted from the fully advanced position, by the biasing force of the biasing device. After the movable member has been retracted to its fully retracted position or lower dead point, the movable member is again advanced by the drive force produced by the drive device. The biasing device is desirably arranged to hold the movable member in pressing contact with the drive device.
The biasing force Fs of the biasing device is smaller than the drive force Fd produced by the drive device. Namely, Fs less than Fd. Accordingly, when the friction force Ff acting on the movable member based on the deformation of the wall of the support member becomes larger than the biasing force Fs, that is, when Ff greater than Fs, the retracting movement of the movable member is inhibited by the friction force, in the absence of the drive force acting on the movable member. As a result, the movement of the movable member is eventually inhibited at the fully advanced position. It is also noted that the pressure of the pressurized fluid delivered by the pump device is the highest when the movable member is located at its fully advanced position. Accordingly, the movable member is held stationary at the fully advanced position with high stability, where the movement restricting device is arranged to restrict the movement of the movable member on the basis of the pressurized fluid delivered by the pump device. Where the movement restricting device is arranged to restrict the movement of the movable member on the basis of an electromagnetic force as described above with respect to the above mode (16), the movement of the movable member can be inhibited at any desired position, by controlling the amount of electric current to be applied to the coil of the electromagnetically operated device so that the friction force based on the electromagnetic force is larger than the biasing force of the biasing device.
The friction force required to be applied to the movable member on the basis of the deformation of the wall for inhibiting the movement of the movable member is reduced by reducing the biasing force of the biasing device.
(18) A pump device according to any one of the above-modes (1)-(17), further comprising a drive device operable in contact with the movable member, to advance the movable member, and wherein the drive device includes a drive member not connected to the movable member.
In the pump device according to the above mode (18) wherein the drive member of the drive device is not connected to the movable member, the movable member is held stationary at the fully advanced position while the drive member is returned in the retracting direction, after the movement of the movable member is inhibited at the fully advanced position. After the movement is inhibited, therefore, a load acting on the drive device is reduced, so that the required amount of consumption of the energy by the drive device is accordingly reduced.
(19) A pump device according to any one of the above modes (1)-(18), further comprising a fluid sucking portion, and wherein the movable member partially defines a pump chamber in front of the movable member, and carries a suction valve operable between a first state for permitting a flow of the working fluid into the pump chamber through the fluid sucking portion, and a second state for inhibiting the flow of the working fluid into said pump chamber.
(20) A pump device according to the above mode (19), wherein the suction valve includes a valve seat formed on a front end face of the movable member, a valve member movable toward and away from the valve seat according to a difference between pressures of the fluid in the fluid sucking portion and the pump chamber, and a holder member for holding the valve member, the holder member having an internal dimension which is smaller at a position relatively distant from the valve seat, than at a position relatively near the valve seat.
In the pump device according to the above mode (20), the valve member is held by the holder member such that the valve member is movable toward and away from the valve seat. Further, the internal dimension of the holder member is made smaller at a position relatively distant from the valve seat. This arrangement makes it possible to reduce an amount of misalignment of the valve member with respect to the movable member in the radial direction of the movable member when the valve member is spaced apart from the valve seat. If the internal radial dimension (diameter) of the holder member were substantially constant in the axial direction, it would be necessary to provide a spring for biasing the valve member toward the valve seat, to thereby prevent radial misalignment of the valve member with respect to the movable member. In the present pump device, however, the holder member eliminates a need to provide such a spring for preventing the radial misalignment of the valve member, and assures leakage-free seating of the valve member on the valve seat even in the absence of a spring.
The internal radial dimension (diameter) of the holder member may be reduced either continuously or in steps in the axial direction away from the valve seat. In the former case, the holder member may have a tapered inner surface.
(21) A pump device according to any one of the above modes (1)-20), wherein the movable member consists of a plurality of separate movable members which are fitted in respective fitting recesses of the support member.
While the pump device may use only one movable member, the pump device usually uses a plurality of movable members, which are disposed radially, or in parallel or series with each other. The movements of all of the movable members may be inhibited at the same time. Alternatively, the movement of at least one of the movable members is inhibited at a point of time different from that at which the movement of the other movable member or members is inhibited.
(22) A pump device according to the above mode (21), wherein the movement restricting device restricts the movement of at least one of said plurality of separate movable members at a point of time different from that at which the movement of the other movable member or members is restricted.
In the pump device according to the above mode (22), the movement of at least one of the movable members is restricted at a point of time different from that at which the movement of the other movable member or members is restricted. This arrangement permits a change of the amount of the pressurized fluid to be delivered by the pump device, for a given pressure of the pressurized fluid. The pressure of the pressurized fluid can be increased, at a smaller amount of energy consumption by the pump device, when the amount of the pressurized fluid is reduced, than when the amount of the pressurized fluid is not reduced (namely, is maintained at the nominal value). In a fluid-actuated device operated by the pressurized fluid delivered by the pump device, the required amount of the pressurized fluid is usually smaller when the pressure of the pressurized fluid is relatively high than when the pressure is relatively low. The required size of the drive device for reciprocating the movable members can be made smaller where the amount of the pressurized fluid is controlled to be relatively large when the pressure of the pressurized fluid is relatively low and to be relatively small when the pressure is relatively high, than where the nominal amount of pressurized fluid is delivered irrespective of the pressure of the pressurized fluid.
Where the movements of the plurality of movable members are restricted at respective different points of time, the amount of the pressurized fluid to be delivered by the pump device can be changed in steps.
(23) A pump device according to any one of the above modes (1)-(22), comprising at least one of a piston pump and a vane pump.
The piston pump includes a plunger pump, which includes an axial plunger pump, a radial plunger pump, and double-acting plunger pump. The axial plunger pump is constructed such that a piston is reciprocated by rotation of a swash plate. The radial plunger pump includes a radial array of a plurality of pistons. The double-acting plunger pump includes a plurality of pistons arranged in parallel with each other.
Where the pump device is a vane pump, the movable member consists of a plurality of vanes slidably fitted in respective grooves formed in a rotor. During rotation of the rotor, the vanes are reciprocated within the respective grooves while the vanes are held at their end faces in sliding contact with the inner circumferential surface of a housing which accommodates the rotor. In this case, the movement restricting device is arranged to restrict or inhibit the reciprocating movements of the vanes in the grooves. When the reciprocating movements in the grooves are inhibited, the working fluid is not pressurized even while the rotor is rotated.
(24) A pump device according to any one of the above modes (1)-(23), which is provided in a braking system for a vehicle, to supply a wheel brake cylinder with the pressurized fluid, to brake a wheel of the vehicle.
(25) A pump device including a support member having a fitting recess, and a movable member which is reciprocated in said fitting recess to suck a working fluid, pressurize the fluid and deliver the pressurized fluid, said pump device comprising a movement restricting device operable to deform a wall at least partially defining the fitting recess of the support member, such that the wall is deformed inwardly of the fitting recess, for restricting a reciprocating movement of the movable member in the fitting recess, and such that an amount of deformation of the wall is larger when an amount of the pressurized fluid required to be delivered by the pump device is relatively small than when the amount is relatively large.
In the pump device according to the above mode (25), the movement restricting device may be arranged not to deform the wall when the requirement to deliver the pressurized fluid is relatively high, and to deform the wall by a predetermined constant amount when the required amount of delivery of the pressurized fluid by the pump device is smaller than the nominal delivery amount. Alternatively, the movement restricting device is arranged such that the amount of deformation of the wall changes with the required amount of delivery of the pressurized fluid by the pump device.
It is to be understood that the pump device according to the above mode (25) may incorporate the technical feature of any one of the above modes (1)-(24) described above.
(26) A pump device comprising a support member having a fitting recess, and a movable member which is reciprocated in said fitting recess to suck a working fluid, pressurize the fluid and deliver the pressurized fluid, characterized by further comprising a pressing device operable to apply a pressing force to the movable member in a direction intersecting a direction of reciprocation of the movable member, when an amount of the pressurized fluid required to be delivered by the pump device is smaller than a nominal delivery amount of the pump device.
In the pump device according to the above mode (26), a reciprocating movement of the movable member is inhibited when a force of friction acting on the movable member on the basis of the pressing force produced by the pressing force becomes larger than a force by which the movable member is moved. It will be understood that the pump device according to the above mode (26) may incorporate the technical feature according to any one of the above modes (1)-(25) described above.
(27) A pump device comprising a support member having a fitting recess, and a movable member which is reciprocated in said fitting recess to suck a working fluid, pressurize the fluid and deliver the pressurized fluid, characterized by further comprising a clamping device operable to deform a wall at least partially defining the fitting recess of the support member, such that said wall is deformed inwardly of the fitting recess, for clamping the movable member at a non-delivery position thereof, at least when an amount of the pressurized fluid to be delivered by the pump device is smaller than a nominal delivery amount of the pump device, the amount of the pressurized fluid delivered by the pump device being zero when said movable member is located at said non-delivery position.
In the pump device according to the above mode (27), the movable member is clamped at its non-delivery position when the amount of the pressurized fluid required to be delivered by pump device is smaller than the nominal delivery amount. In a piston pump device, the amount of the pressurized fluid delivered by the pump device is zero when the piston is located at its fully advanced position. In a vane pump device, the amount of pressurized fluid delivered by the pump device is zero when the vane is located at its fully retracted position on the radially inner side of the rotor. That is, the non-delivery position is the fully advanced position of the piston in the piston pump device, and the fully retracted position of the vane in the vane pump device. It will be understood that the pump device according to the above mode (27) may incorporate the technical feature according to any one of the above modes (1)-(26).